404 



GENERAL BIOLOGY 



split the anther tube of the dandelion, and spread it out flat 

 before covering (fig. 236). When the pollen cavities are so 

 filled that they appear dark, a little pressure on the cover 

 will often burst them and scatter the pollen, so that it 



may be counted. 



The gist of this study is 

 in the ratios of the last 

 column. For ready com- 

 parison they should be 

 reduced to the form x:i. 



With perfect flowers the 

 ratio of pollen grains to 

 ovules produced will be the 

 same for the whole plant as 

 for the single flower, but 

 with monoecious (fig. 235) 

 and dioecious species it will 

 be necessary to count and 

 estimate for equivalent pro- 

 portions of the total of male 

 and female inflorescence. 



The record. In conclu- 

 sion, ascertain from the 

 facts of the completed 

 table whether the form of 

 the cluster or the manner of flower aggregation in it have 

 had any effect on the amount of pollen produced. 



FIG. 236. A single dandelion removed 

 from the flower head. /, stigma; k, 

 the anther ring, split and unrolled at o, 

 the separate filaments shown at p: 

 n, strap-shaped corolla; /, calyx (pap- 

 pus) of bristles; m, ovule case. 



III. ADJUSTMENT IN FORM AND APPEARANCE. 



When we have gotten to this division of our subject, it has 

 -already been illustrated in manifold ways by the organisms 

 we have had before us. Nevertheless, it will still repay a 

 more careful examination. 



